1. Field of the Invention
The invention relates to a needle bar draw frame, also termed or known as gill box for slivers comprising a needle field resp. gill area of needle bars carried by chains, entry rollers lying upstream of the needle field, drawing rollers disposed downstream of the needle field, and controlling elements for the slivers arranged above the needle field and extending resp. dipping in between the needles of the needle bars.
2. Description of Prior Art
Needle bar draw frames with an upper needle field as a controlling element enable bringing the fibres in agreeable parallelism and homogenising a fed sliver correctly, but also present a series of disadvantages. E.g., it is not possible in the case of a double draw field consisting of a lower and an upper needle field to achieve an adequately short nip for the processing particularly of short-staple slivers, which is the reason that the degree of parallelism attainable in the processing of long-staple slivers cannot be reached thereby. Although this disadvantage may be avoided when using single needle fields, it is, however, substituted by another disadvantage, which lies in that the sliver dipping into the needle field tends to extend beyond the tips of the needles, whereby parts of the sliver are withdrawn from the influence of the needles. Therefore, controlling elements have been arranged in the shape of one or more cage cylinders or rollers above the needle field, as disclosed by DE-GM No. 74 26 839, which are driven at a peripheral speed corresponding to the advancing motion of the needle field and, with their bars, protrude between the needle rows of the needle field.
Furthermore DE-PS No. 611 914 discloses a needle bar draw frame, in which a bar belt is mounted above the needle field, the bars of which in like manner protrude between the needle rows of the needle field.
The desired effect is however attained only in part by these devices, because it has become evident that due to the constructional conditions, a zone not controllable by these means remains shortly before the take-off roller pair, which makes a processing particularly of short-staple slivers more difficult.
3. Object of the Invention
It is therefore a main object of the invention to remove this defect by improving the known needle bar draw frames with single needle field so that they are in a position of attaining the intended perfect effect of parallelism of the fibres even in the case of voluminous slivers with short-staple fibres at high delivery speeds and high drafts.